Turning the lights back on...

[Jack]

If the population suffers a massive loss through natural or otherwise disaster our power, sanitation, telecoms, transport and other utilities and infrastructure will grind to a halt.
What of them would be in your opinions the most vital to switch back on?
As most systems rely on computers I would think power would be the most important, given that most of us wouldn't know where to start in any power plant in the running and maintainence of I suppose localised generators hooked up to other facilities would be the most logical move until the skills needed could be developed to get the chimneys stoked... What then would you dedicate your limited resources (generators and fuel)?
Transport is a good one, namely rail, as communications trade and aid could be delivered in person and on mass.
Communications would be vital and I'm led to believe from telecoms engineers that there are built in fail safes designed to operate with little or no input from engineers though the system dates back to pre 1950's tech so unsure on reliability, plus these are wired lines are for military and government use only. as a foot note on telecoms many exchanges (buildings that house the equipment) have lead lined and deep shelters complete with hardened vault doors (can confirm they exist as was shown).
Sanitation is an obvious need though we can manage without for a time before populations increase, having running clean water has its obvious advantages to living and indeed in summer months for watering crops with hoses hooked up to the mains.
I mentioned law enforcement/security in another thread in the form of militia so won't cover that here and just imply this has already been established.
Hospitals and pharmacists would be ransacked and medical supplies all but gone by the time people where organised to begin thinking of rebuilding so I imagine that we would rely on herbal remedies and some basic chemistry for developing penicillin and other antibiotics.
So, I'm not entirely sure, if it where up to me I believe that getting transport running would be for the best to begin with and the rest would follow as you scour the nation for survivors that have the skills to operate and train others to do so in places such as power plants and water treatment.
But if you had to choose which to focus on, which we could do without or completely rethink, what would they be, how would you do it?